One principal objective of this program of research is to redefine concepts of cognitive psychology and human learning in terms of operations of measurement of individual differences. Another major section of the study is directed at elucidating the functions of speediness and carefulness in performances on intellectual tasks. Measurements developed in accordance with these orientations are to be studied within the context of a broad sampling of the abilities which have defined fluid and crystallized intelligence, as well as functions associated with input modality (visualization), span of awareness and retrieval. The measurements are to be studied also within the context of development, particularly development in adulthood. One aim in this is to provide an improved theory and more detailed description of the principal cognitive functions in respect to which there are notable individual differences. The aim is also to provide an improved basis of knowledge about the kinds of abilities which do, and do not, decline during the adult years.